Auto focus adjusting method, auto focus adjusting apparatus, and digital photographing apparatus including the same

ABSTRACT

An auto focus (AF) adjusting method, an AF adjusting apparatus, and a digital photographing apparatus including the same, the AF adjusting apparatus including: an AF calculator for calculating focus detection evaluation values; a peak detector for detecting a peak position of the focus detection evaluation values; and a speed calculator for calculating a moving speed of a subject by using the peak position. When continuous photographing of still images is performed, the peak detector detects the peak position in an image pickup interval before a light exposure preparation interval for image capturing, and the focus lens driver performs moving body compensation driving for compensating for a focal position by using a moving speed calculated in the light exposure preparation interval before capturing starts.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/566,002, filed Aug. 3, 2012, now U.S. Pat. No. 9,152,010, whichclaims the benefit of Korean Patent Application No. 10-2011-0078201,filed on Aug. 5, 2011, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entirety byreference.

BACKGROUND

1. Field

The invention relates to an auto focus (AF) adjusting method, an AFadjusting apparatus, and a digital photographing apparatus including thesame.

2. Description of the Related Art

In digital photographing apparatuses, such as cameras and camcorders, aswell as smartphones and other devices that include a digital imagingmodule, to capture a clear still image or a clear moving picture, it isimportant to correctly focus on a subject. There is a contrast autofocus (AF) method and a phase difference AF method as for automaticallyperforming focus adjustment.

The contrast AF method is a method of acquiring contrast values withrespect to image signals generated from an image pickup sensor whileperforming photographing by changing a position of a focus lens, anddriving the focus lens to a focus lens position of a peak contrastvalue. However, because it takes time to detect a peak position, that isa focal position in the contrast AF method, it is not easy to focus whena moving subject is photographed.

SUMMARY

An embodiment of the invention provides an auto focus (AF) adjustingmethod and an AF adjusting apparatus, whereby a moving subject can bequickly and correctly focused by using a contrast AF method even whencontinuous photographing is performed, and a digital photographingapparatus including the same

According to an embodiment, there is provided an auto focus (AF)adjusting apparatus including: an image pickup lens in which theposition of a focus lens is variable for focus adjustment; a focus lensdriver for driving the focus lens; an image pickup device for generatingan image signal by picking up light which has passed through the imagepickup lens; an AF calculator for calculating focus detection evaluationvalues from the image signal; a peak detector for detecting the peakposition of the focus detection evaluation values; a shutter forcontrolling light exposure of the image pickup device; and a speedcalculator for calculating the moving speed of a subject by using thepeak position, wherein, when continuous photographing for continuouslycapturing still images is performed, the peak detector detects the peakposition in an image pickup interval before a light exposure preparationinterval for image capturing, and the focus lens driver performs movingbody compensation driving for compensating for a focal position by usinga moving speed calculated in the light exposure preparation intervalbefore capturing starts.

The shutter may be a mechanical shutter including a front curtain and arear curtain.

The moving body compensation driving may be performed before driving tochange the shutter to a closed state is completed.

The shutter may be an electronic front curtain shutter including anelectronic front curtain for beginning light exposure by resettingelectric charges and a mechanical rear curtain for ending the lightexposure.

The moving body compensation driving may be performed in an intervalbefore beginning to drive the front curtain for image capturing afterstopping driving for selectively reading electric charges from the imagepickup device.

Alternatively, the shutter may be a global shutter including anelectronic front curtain for beginning light exposure by resettingelectric charges and an electronic rear curtain for ending the lightexposure.

Alternatively, the moving body compensation driving may be performed inan interval before beginning to drive the front curtain for imagecapturing after stopping driving for selectively reading electriccharges from the image pickup device.

The AF adjusting apparatus may end displaying before image capturing,and the moving body compensation driving may be performed in an intervalbefore beginning the image capturing after ending the displaying.

The detection of the peak position may be performed by driving the focuslens back and forth.

During continuous photographing, detecting a peak position multipletimes may be performed in the image pickup interval before the lightexposure preparation interval, and the moving speed of the subject maybe calculated from a result of the detecting of a peak position multipletimes.

During continuous photographing, the peak position detection may beperformed at least once in the image pickup interval before the lightexposure preparation interval for every image capturing, and the movingspeed of the subject may be calculated by using a peak position resultdetected in the image pickup interval for current image capturing and apeak position result detected in the image pickup interval for previousimage capturing.

During continuous photographing, when the moving speed of the subject isfast, the peak position detection may be performed once in the imagepickup interval before the light exposure preparation interval, and whenthe moving speed of the subject is slow, the peak position detection maybe performed multiple times in the image pickup interval before thelight exposure preparation interval.

During continuous photographing, the moving speed of the subject may bedetermined by using the moving speed of the subject acquired until thecontinuous photographing starts or the moving speed of the subjectobtained in previous capturing during the continuous photographing.

When the moving speed of the subject is acquired before the continuousphotographing starts, the acquired moving speed and a moving speed ofthe subject acquired during the continuous photographing may both beused to predict the peak position in capturing. But when the movingspeed of the subject is not acquired before the continuous photographingstarts, the moving speed of the subject acquired during the continuousphotographing may be used to predict the peak position in capturing.

The moving body compensation driving may be performed by predicting thepeak position from the moving speed of the subject and a time untilcapturing.

When the moving speed of the subject is acquired, the moving bodycompensation driving may be performed by predicting the peak positionaccording to movement of the subject in an interval from a lightexposure end time to an image pickup start time before the lightexposure preparation interval for image capturing by using the acquiredmoving speed.

According to another embodiment, there is provided an auto focus (AF)adjusting method of an AF adjusting apparatus capable of continuousphotographing in which still images are continuously captured, the AFadjusting method including: generating an image signal by picking uplight from a subject; calculating focus detection evaluation values fromthe image signal; detecting the peak position of the focus detectionevaluation values in an image pickup interval before a light exposurepreparation interval for image capturing during the continuousphotographing; calculating the moving speed of the subject by using thepeak position; and compensating for the focal position by using themoving speed calculated in the light exposure preparation interval.

According to another embodiment, there is provided a digitalphotographing apparatus capable of performing auto focus (AF)adjustment, the digital photographing apparatus including: an imagepickup lens in which the position of a focus lens is variable for focusadjustment; a focus lens driver for driving the focus lens; an imagepickup device for generating an image signal by picking up light whichhas passed through the image pickup lens; an AF calculator forcalculating focus detection evaluation values from the image signal; apeak detector for detecting the peak position of the focus detectionevaluation values; a shutter for controlling light exposure of the imagepickup device; and a speed calculator for calculating the moving speedof a subject by using the peak position, wherein, when continuousphotographing for continuously capturing still images is performed, thepeak detector detects the peak position in an image pickup intervalbefore a light exposure preparation interval for image capturing, andthe focus lens driver performs moving body compensation driving forcompensating for a focal position by using the moving speed calculatedin the light exposure preparation interval before capturing starts.

When the moving speed of the subject is acquired, the moving bodycompensation driving may be performed by predicting the peak positionaccording to movement of the subject in an interval from a lightexposure end time to an image pickup start time before the lightexposure preparation interval for image capturing by using the acquiredmoving speed.

According to the above-described configuration, an AF adjustingapparatus and a digital photographing apparatus including the sameaccording to embodiments of the invention can quickly and correctlyfocus on a moving subject even when continuous photographing isperformed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent bydescribing in detail exemplary embodiments thereof with reference to theattached drawings in which:

FIG. 1 is a block diagram of a digital photographing apparatus accordingto an embodiment;

FIG. 2 is a block diagram of a camera controller according to anembodiment;

FIGS. 3A, 3B, 3C, and 3D illustrate graphs to describe an auto focus(AF) operation in a contrast AF method;

FIG. 4 is an AF operation timing diagram of the digital photographingapparatus according to an embodiment;

FIG. 5 is a timing diagram indicating a relationship between operationtiming of the digital photographing apparatus and a position of a focuslens;

FIG. 6 is a graph that illustrates performing moving body prediction AF,according to an embodiment;

FIG. 7 is a graph to describe a method of performing moving bodyprediction AF, according to another embodiment;

FIGS. 8A, 8B, 8C, 8D, 8E, 8F, and FIG. 8G are timing diagrams of themoving body prediction AF performed with reference to FIG. 7;

FIG. 9 is a timing diagram indicating a moving body compensation drivingmethod according to an embodiment;

FIGS. 10 to 14 are timing diagrams indicating a moving body compensationdriving method according to other embodiments;

FIG. 15 is a flowchart illustrating a method of controlling the digitalphotographing apparatus, according to an embodiment;

FIGS. 16 and 17 are flowcharts illustrating a method of controlling thedigital photographing apparatus, according to another embodiment;

FIGS. 18, 19A, and 19B are flowcharts illustrating a method ofcontrolling the digital photographing apparatus, according to anotherembodiment;

FIGS. 20A and 20B are flowcharts illustrating another embodiment of FIG.19B; and

FIG. 21 is a flowchart illustrating another embodiment of FIGS. 19A and19B.

DETAILED DESCRIPTION

The invention may allow various changes or modifications and variouschanges in form, and exemplary embodiments will be illustrated indrawings and described in detail in the specification. However, itshould be understood that the exemplary embodiments do not limit theinventive concept to a specific disclosing form but include everymodified, equivalent, or replaced from within the spirit and scope ofthe invention.

Hereinafter, exemplary embodiments are shown and described. Likereference numerals in the drawings denote like elements, and thus theirrepetitive description will be omitted.

[Configuration and Operation of a Digital Photographing Apparatus 1]

Referring to FIG. 1, the digital photographing apparatus 1 includes aninterchangeable lens 100 and a main body 200. The interchangeable lens100 includes a focus detection function, and the main body 200 includesa function of controlling the interchangeable lens 100 to drive a focuslens 104.

The interchangeable lens (hereinafter referred to as lens) 100 includesan image forming optical system 101, a zoom lens position sensing sensor103, a lens driving actuator 105, a focus lens position sensing sensor106, an iris driving actuator 108, a lens controller 110, and a lensmount 109.

The image forming optical system 101 includes a zoom lens 102 for zoomadjustment, the focus lens 104 for changing a focal position, and aniris 107. The zoom lens 102 and the focus lens 104 may each be a lensgroup in which a plurality of lenses are combined. Hereinafter, acombination of the zoom lens 102 and the focus lens 104 is called animage pickup lens.

The zoom lens position sensing sensor 103 and the focus lens positionsensing sensor 106 sense positions of the zoom lens 102 and the focuslens 104, respectively. Timing for sensing the position of the focuslens 104 may be set by the lens controller 110 or a camera controller209, which will be described below. For example, the timing for sensingthe position of the focus lens 104 may be timing for performing autofocusing (AF) detection from an image signal.

The lens driving actuator 105 and the iris driving actuator 108 drivethe zoom lens 102 and the focus lens 104 and the iris 107 under controlof the lens controller 110, respectively. Specifically, the lens drivingactuator 105 drives the focus lens 104 in an optical axis direction.That is, the lens driving actuator 105 may be an example of a focus lensdriver.

The lens controller 110 transmits the sensed position information of thefocus lens 104 to the main body 200. When the position of the focus lens104 varies, or when the camera controller 209 requests for the positioninformation of the focus lens 104, the lens controller 110 can transmitthe sensed position information of the focus lens 104 to the main body200.

The lens mount 109 includes lens-side communication pins engaged withcamera-side communication pins, which are described below, to be used asa communication path of data, a control signal, etc.

A configuration of the main body 200 will now be described.

The main body 200 may include a view finder (EVF) 201, a shutter 203, animage pickup device 204, an image pickup device controller 205, adisplay unit 206, a manipulation unit 207, the camera controller 209,and a camera mount 208.

The EVF 201 may include a Liquid Crystal Display (LCD) 202, to displayan image during image pickup in real time.

The shutter 203 determines the time for exposing the image pickup device204 to light, i.e., an exposure time. Although both a front curtain anda rear curtain of the shutter 203 are mechanical in FIG. 1, the shutter203 is not limited thereto. For example, the shutter 203 may be anelectronic front curtain shutter including an electronic front curtainfor beginning light exposure by resetting accumulated electric chargesand a mechanical rear curtain. Alternatively, the shutter 203 may be aglobal shutter including an electronic front curtain beginning lightexposure by resetting accumulated electric charges and an electronicrear curtain for ending the light exposure by transmitting accumulatedelectric charges to a light non-exposure part.

The image pickup device 204 generates an image signal by picking upimage light which has passed through the image forming optical system101 of the lens 100. The image pickup device 204 may include a pluralityof photoelectric conversion elements arranged in a matrix form and avertical or/and horizontal transmission line for reading an image signalby moving electric charges from the plurality of photoelectricconversion elements. For the image pickup device 204, a Charge-CoupledDevice (CCD) sensor, a Complementary Metal Oxide Semiconductor (CMOS)sensor, or other image sensor may be used.

The image pickup device controller 205 generates a timing signal andcontrols the image pickup device 204 to pick up an image bysynchronizing the timing signal. In addition, the image pickup devicecontroller 205 sequentially reads an image signal as electric chargeaccumulation to scanning lines ends. The read image signal is used forAF detection by the camera controller 209.

The display unit 206 displays various kinds of images and information.For the display unit 206, an Organic Light Emitting Diode (OLED)display, a Liquid Crystal Display (LCD), or the like may be used. Thedisplay unit 206 may temporarily stop displaying a live-view imagebefore capturing a still image.

The manipulation unit 207 allows a user to input various kinds ofinstructions for operating the digital photographing apparatus 1. Themanipulation unit 207 may include various buttons such as a shutterrelease button, a main switch, a mode dial, and a menu button.

The camera controller 209 calculates a contrast value and performs AFdetection using an image signal generated by the image pickup device204. In addition, the camera controller 209 stores a contrast value atevery AF detection time in response to the timing signal generated bythe image pickup device controller 205 and calculates a focal positionusing the lens position information received from the lens 100 and thestored contrast value. A calculation result of the focal position istransmitted to the lens 100.

The camera mount 208 includes the camera-side communication pins. Inaddition, power may be supplied to the lens controller 110 via thecamera mount 208.

An operation of the lens 100 and the main body 200 will now bedescribed.

When an image is to be captured, an operation of the digitalphotographing apparatus 1 is started by manipulation of the main switchof the manipulation unit 207. The digital photographing apparatus 1performs a live view display as described below.

Image light of the subject, which has passed through the image formingoptical system 101, is incident on the image pickup device 204. At thistime, the shutter 203 is open. The incident image light is convertedinto an electrical signals by the image pickup device 204, therebygenerating an image signal. The image pickup device 204 operates by atiming signal generated by the image pickup device controller 205. Thegenerated image signal of the subject is converted into displayable databy the camera controller 209 and is output to the EVF 201 and thedisplay unit 206. This operation is the live view display, and live viewimages displayed by the live view display may be continuously displayedas a moving picture.

After the live view display is performed, if the shutter release button,one component of the manipulation unit 207, is pressed in a half-pressedstate the digital photographing apparatus 1 starts an AF operation. TheAF operation is performed using the image signal generated by the imagepickup device 204. In a contrast AF method, a focal position iscalculated from a focus detection evaluation value (hereinafter,referred to as ‘AF evaluation value’) associated with a contrast value,and the lens 100 is driven based on the calculation result. The AFevaluation value is calculated by the camera controller 209. The cameracontroller 209 calculates information for control of the focus lens 104from the AF evaluation value and transmits the information to the lenscontroller 110 via the lens-side and the camera-side communication pinsincluded in the lens mount 109 and the camera mount 208, respectively.

The lens controller 110 performs AF by driving the focus lens 104 in anoptical axis direction by controlling the lens driving actuator 105based on the received information. The position of the focus lens 104 ismonitored by the focus lens position sensing sensor 106, therebyestablishing a feedback control.

When the zoom lens 102 zooms according to a user's operation, the zoomlens position sensing sensor 103 senses the position of the zoom lens102, and the lens controller 110 performs AF again by modifying AFcontrol parameters of the focus lens 104.

When an image of the subject is in complete focus, the digitalphotographing apparatus 1 performs light exposure in a fully-pressedstate of the shutter release button. At this time, the camera controller209 fully closes the shutter 203 and transmits measured lightinformation acquired up to that time to the lens controller 110 as iriscontrol information. The lens controller 110 controls the iris drivingactuator 108 based on the iris control information to operate the iris107 to a proper iris value. The camera controller 209 controls theshutter 203 based on the measured light information to capture an imageof the subject by opening the shutter 203 for a proper exposure time.

The captured image is image signal processed (and which may becompressed) and stored on a memory card (212 of FIG. 2). At the sametime, the captured image is output to the EVF 201 and the display unit206 to display a subject. Such an image is called a quick view image.

[Configuration of the Camera Controller 209]

Referring to FIG. 2, the camera controller 209 may include apre-processor 220, a signal processor 221, a compression anddecompression unit 222, a display controller 223, a Central ProcessingUnit (CPU) 224, a memory controller 225, an audio controller 226, a cardcontroller 227, a timer 228, and a main bus 230.

The camera controller 209 provides various kinds of instructions anddata to each component of the camera controller 209 via the main bus230.

The pre-processor 220 receives an image signal generated by the imagepickup device 204 and performs calculation of Auto White Balance (AWB),Auto Exposure (AE), and AF. The pre-processor 220 calculates an AFevaluation value for focus adjustment, an AE evaluation value forexposure adjustment, and an AWB evaluation value for white balanceadjustment. The pre-processor 220 may be an example of an AF calculator.

The signal processor 221 performs a series of image signal processingoperations, such as gamma compensation, to generate a live view image ora captured image displayable on the display unit 206.

The compression and decompression unit 222 performs compression anddecompression of an image signal on which image signal processing hasbeen performed. In the case of compression, an image signal iscompressed in a compression format such as, for example, JointPhotographic Experts Group (JPEG) compression format or H.264compression format. An image file including image data generated by thecompression processing is transmitted to and recorded in a memory card212.

The display controller 223 controls the image output to a display screensuch as the LCD 202 of the EVF 201 or the display unit 206.

The CPU 224 generally controls an operation of each component of thecamera controller 209. In addition, in the case of the digitalphotographing apparatus 1 illustrated in FIG. 1, the CPU 224 performscommunication with the lens 100.

According to the current embodiment, the CPU 224 may detect a peakposition of each AF evaluation value from AF evaluation valuescalculated by the pre-processor 220. In addition, the CPU 224 maycalculate the moving speed of a subject by using the detected peakpositions. That is, the CPU 224 may be an example of a peak detector anda speed calculator. However, the invention is not limited thereto, andanother component may perform the peak detection and speed calculationfunction instead of the CPU 224.

The memory controller 225 controls a memory 210 to temporarily recorddata such as a captured image or associated information, and the audiocontroller 226 controls a microphone or speaker 211. The card controller227 controls the memory card 212 to record captured images.

The timer 228 measures time.

Although it has been described with reference to FIGS. 1 and 2 that thelens 100 is an exchangeable lens detachably attached to the main body200, the invention is not limited thereto. For example, the digitalphotographing apparatus 1 may include the lens 100 and the main body 200one integrated body. In this case, the lens mount 109 and the cameramount 208 may be excluded, and the camera controller 209 may perform afunction of the lens controller 110. For example, the camera controller209 may directly control the lens driving actuator 105 and the irisdriving actuator 108 and receive position information from the zoom lensposition sensing sensor 103 and the focus lens position sensing sensor106.

[AF Operating Method]

FIGS. 3A, 3B, 3C, and 3D illustrate an AF operation according to anembodiment of the contrast AF method. In the contrast AF method, the AFoperation is performed by repeatedly calculating an AF evaluation valueassociated with a contrast value from an image signal and detecting afocal position with a position of the focus lens 104 at which acalculated AF evaluation value is a maximum value. Each horizontal axisof FIGS. 3A, 3B, 3C, and 3D indicates a position of the focus lens 104,and each vertical axis indicates an AF evaluation value.

First, as shown in FIG. 3A, to detect a peak of AF evaluation value,scanning is performed by high-speed driving the focus lens 104 from oneside to the other side (hereinafter, referred to as ‘operation A’).Here, the scanning indicates calculating an AF evaluation value whiledriving the focus lens 104. An approximate peak position is detected byoperation A.

Thereafter, as shown in FIG. 3B, the peak detection is performed againby reversing the driving direction of the focus lens 104 and more slowlydriving the focus lens 104 than during operation A (hereinafter,referred to as ‘operation B’). AF detection may be performed byoperation B at a higher accuracy than operation A.

Thereafter, as shown in FIG. 3C, the driving direction of the focus lens104 is reversed again, and the focus lens 104 is driven towards thefocal position according to the detected peak (hereinafter, referred toas ‘operation C’). At this time, a device for driving a lens usually hasa backlash causing an error of a lens position according to a drivingdirection. Thus, the backlash needs to be removed, and in operation C,the focus lens 104 is driven over the focal position.

Finally, as shown in FIG. 3D, the driving direction of the focus lens104 is reversed again, and the focus lens 104 is driven in the samedirection as the driving direction according to operation B to stop atthe focal position (hereinafter, referred to as ‘operation D’).

According to embodiments of the invention, AF evaluation values arecalculated by performing a scanning operation even in operation C, andthe calculated AF evaluation values are used to detect movement of asubject.

The AF operation is performed by operations A to D.

[Operation of the Digital Photographing Apparatus 1]

FIG. 4 is an AF operation timing diagram of the digital photographingapparatus 1 according to an embodiment.

Referring to FIG. 4, timing diagrams of an accumulation start signal, anelectric charge accumulation signal of a first scanning line, AFarea[1]to AFarea[a] electric charge accumulation signals used for AF detection,an electric charge accumulation signal of an nth scanning line, and areading start signal are sequentially shown from the top. Together withthe plurality of timing diagrams, an AF evaluation value calculationtiming diagram, a lens synchronization position of a central position ofan image for which an AF evaluation value calculation is performed, andposition information of the focus lens 104 at a timing corresponding tothe lens synchronization position are shown. Here, AFarea[1] toAFarea[a] denote scanning lines included in an area for which AFdetection is performed.

When accumulation start signals P1, P2, . . . are applied, electriccharges are accumulated due to image light incident on first to nthscanning lines. At times when electric charge accumulation of the firstscanning line ends, reading start signals S1, S2, . . . of an imagesignal are generated. Due to the reading start signals S1, S2, . . . ,image signals are sequentially read from the first scanning line. Theread image signals are transmitted to the camera controller 209. Attimes when electric charge accumulation of AFarea[1] to AFarea[a]included in an AF detection area ends, AF evaluation values V1, V2, . .. are calculated using the image signals read by the pre-processor 220.While calculating the AF evaluation values V1, V2, . . . , the focuslens 104 continuously moves at a constant speed.

In the current embodiment, at a time when a fourth AF evaluation valueV4 is calculated, it is determined that the fourth AF evaluation valueV4 is less than a previous AF evaluation value, i.e., that the fourth AFevaluation value V4 has passed a peak position. Thus, as shown in FIG.4, from this time, the focus lens 104 is driven in a reverse direction.That is, at the time when the fourth AF evaluation value V4 iscalculated, the AF operation proceeds from operation A to operation B.The operations C and D follow similarly.

FIG. 5 is a timing diagram indicating the relationship between operationtiming of the digital photographing apparatus 1 and the position of thefocus lens 104. The horizontal axis indicates time, and the verticalaxis sequentially indicates from the top a position of the focus lens104, a half-press signal S1 of the shutter release button, a full-presssignal S2 of the shutter release button, an image view signal IMAGE VIEWfor displaying a captured image, a shutter signal SHUTTER, an irissignal DIAPHRAGM, a light exposure signal EXPOSE for the image pickupdevice 204, and a data read signal. In the current embodiment, a casewhere the half-press signal S1 and the full-press signal S2 areactivated at almost the same time is illustrated.

Referring to FIG. 5, the AF operation starts by the half-press signal S1at a time t0, thereby driving the focus lens 104 at a high, constantspeed. That is, this corresponds to operation A of FIG. 3A. When a peakvalue of AF evaluation values is detected, the focus lens 104 is drivenin a reverse direction at a low, constant speed. That is, thiscorresponds to operation B of FIG. 3B. The peak value of the AFevaluation values is detected by operation B. Thereafter, operation C ofFIG. 3C is performed by reversing the driving direction of the focuslens 104, and finally, operation D of FIG. 3D is performed to removebacklash. Accordingly, the focus lens 104 is at an in-focus position,and the AF operation ends at a time t1.

When the AF operation ends, the display unit 206 stops displaying, andthe shutter 203 is closed. Thereafter, the iris 107 is operated from anopen state to a proper iris value. When a preparation for an imagecapture ends, the shutter 203 is opened, thereby starting light exposureat a time t2.

Here, a time between the in-focus time t1 and the time t2 when theshutter 203 is open for light exposure is called a release time lag. Inthis case, if the full-press signal S2 is activated after in-focus, atime between a time when the full-press signal S2 is activated and thetime t2 when the shutter 203 is open is called the release time lag.

When the shutter 203 is open, light exposure of the image pickup device204 starts at the time t2, and after the light exposure is performed fora proper time, the shutter 203 is closed again at a time t3. Then,electric charges accumulated by the image pickup device 204 aretransmitted to the camera controller 209 to read an image signal.Thereafter, the shutter 203 and the iris 107 are opened again at a timet4 to be in an open state at a time t5.

Meanwhile, when a subject moves in an optical axis direction of theimage pickup lens, there is a time lag between a time when a focalposition is detected and a final in-focus time in operation B of the AFoperation, and accordingly, the subject moves during the time lag.Moreover, the subject also moves in an interval in which the releasetime lag occurs. That is, the subject is not in focus during lightexposure. Thus, in embodiments of the invention, such out-of-focus iscompensated for. In this case, because a focal position of the movingsubject is predicted, this operation is called moving body predictionAF, as will be described now with reference to FIGS. 6 and 7.

FIG. 6 is a graph to describe a method of performing moving bodyprediction AF, according to an embodiment of the invention. Thehorizontal axis indicates a position of the focus lens 104, wherein theright side indicates a near direction. The vertical axis indicates an AFevaluation value. The graph of FIG. 6 shows a distribution of AFevaluation values of a moving body.

Referring to FIG. 6, when the AF operation starts, operation A andoperation B are performed, thereby obtaining an initial AF evaluationvalue peak position. The obtained peak position is B1. Thereafter,operation C is performed, and a peak position is detected by calculatingAF evaluation values. However, the peak position detected by operation Cis an approximate position obtained by subtracting a backlash amountfrom an original peak position.

The peak position detected by operation C is almost the same as B1 whena subject does not move. However, when the subject moves, the peakposition detected by operation C moves to C1. At this time, if B1 isdifferent from C1+BKL (backlash amount), it is determined that thesubject has moved. Thus, operation B is performed again withoutperforming operation D of FIG. 3D. As a result, B2 is detected as a newpeak position. That is, it is determined that the subject is a movingbody and the peak position has moved to B2.

When the subject moves, an image surface speed of the subject iscalculated. When the subject moves at a relatively slow, constant speed,the image surface speed may also approach a constant speed. Thus, aspeed Sv of the subject may be calculated from a transition between thepeak positions B1 and B2 and a time T1 taken for the transitionaccording to the equation below.Sv=(B1−B2)/T1

If it is assumed that the time between when B2 is calculated and whenthe next peak position of AF evaluation values is T2, a focuscompensation value ΔB3 during T2 is obtained by ΔB3=Sv*T2. When thefull-press signal S2 is activated to start a shutter release, acompensation value AR due to the release time lag Tr is also obtained byΔR=Sv*Tr.

By the above-described method, the position Rx of the focus lens 104 atwhich an AF evaluation value at a light exposure start time is a peakposition can be obtained, and the moving body prediction AF is performedby driving the focus lens 104 to the position Rx.

Here, the use of B1 and B2 to obtain Sv is to not include an error dueto a backlash into the calculation. When backlash does not occur eventhough the focus lens 104 is driven in a reverse direction, Sv can becalculated by using the peak position C1 of AF evaluation values that iscalculated in operation C, i.e., Sv=(B1−C1)/T1.

Although the speed of a subject is calculated by using only B1 and B2 inthe current embodiment, an error exists in each AF evaluation value dueto noise. Thus, an average value further including B3 may be used. Thatis, Sv may be obtained by calculating Sv1=(B1−B2)/T1, Sv2=(B2−B3)/T2,and Sv=(Sv1+Sv2)/2. A compensation value ΔB4 during the AF operation maybe obtained from the obtained value Sv by ΔB4=Sv*T3, and thecompensation value ΔR due to the release time lag Tr may also beobtained by ΔR=Sv*Tr.

When the speed of a subject is fast, the following equation may be used.If it is assumed that the focal distance of a front side of the imagepickup lens is f, the focal distance of a rear side thereof is f′, thedistance from the focal position of the front side of the image pickuplens to the subject is d, the distance from the focal position of therear side thereof to an image surface is z, and an image surfaceposition when the subject approaches the digital photographing apparatus1 at a constant speed is Z(t), the following equation can be obtained.

${Z(t)} = \frac{{ff}^{\prime}}{d - {\frac{\mathbb{d}z}{\mathbb{d}t}t}}$

When this equation is approximated to a two-dimensional equation,Z(t)=At²+Bt+C is obtained. By using the time until the next AFevaluation value is calculated or the time due to the release time lagas a value of t, the moving body prediction AF in a release operationmay be performed.

FIG. 7 illustrates a method of performing moving body prediction AF,according to another embodiment. In FIG. 7, the horizontal axisindicates the position of the focus lens 104, and the vertical axisindicates an AF evaluation value. In the current embodiment, a method ofdetecting a focus of a moving body by a wobbling operation is used.

Referring to FIG. 7, LVpk denotes a peak position of AF evaluationvalues, Vpk denotes a peak value of the AF evaluation values, and PKdenotes a peak point on the graph. When the focus lens 104 is minutelyvibrated by dx in an optical axis direction, an AF evaluation value isalso minutely changed by dy. In the current embodiment, a focus of themoving body is detected by using this characteristic.

FIGS. 8A, 8B, 8C, 8D, 8E, 8F, and FIG. 8G are timing diagrams of themoving body prediction AF performed with reference to FIG. 7. In FIGS.8A, 8B, 8C, 8D, 8E, 8F, and FIG. 8G, light exposure by the image pickupdevice 204 is performed once a field (1VD), and the wobbling operationis performed in a fourth period.

FIG. 8A is a timing diagram of a vertical synchronization signal VD,FIG. 8B is a timing diagram of the position of the focus lens 104, FIG.8C is a timing diagram of light exposure, FIG. 8D is a timing diagram ofreading an image signal, FIG. 8E is a timing diagram of the read timingsignal, FIG. 8F is a timing diagram of reading an AF evaluation value,and FIG. 8G is a timing diagram of the lens driving control signal.

First, the focus lens 104 moves from a far direction to a near directionby, for example, 3Fδ, where F denotes the iris value and δ denotes thedepth-of-focus value. An image signal is acquired even when the focuslens 104 is moving. Thereafter, the focus lens 104 stops at a nearposition, and an image signal is acquired. Thereafter, the focus lens104 moves in the far direction and stops. The above-described operationsare performed in a one-field unit and completed by a total of 4 fields.

When the image signal reading by the light exposure of FIG. 8C isperformed, an integral time varies according to brightness. In addition,an image signal acquired during e1 is read at timing VR2 of the nextfield. Each of the operations is achieved within one field.

Thereafter, an AF evaluation value is acquired at timing AF3 of the nextfield, and the control signal is generated at timing LD4 of the nextfield by using the AF evaluation value acquisition result.

The above-described operations correspond to the wobbling operation, andin-focus is achieved at a contrast peak position using theabove-described method.

In the current embodiment, the moving body prediction AF described withreference to FIG. 6 is performed by using the wobbling operation. Thatis, the peak positions B1 and B2 are obtained by performing the wobblingoperation.

Hereinafter, an operation of the digital photographing apparatus 1 towhich the moving body prediction AF is applied will be described.

FIG. 9 is a timing diagram indicating a moving body compensation drivingmethod according to an embodiment of the invention. In the timingdiagram of FIG. 9, the horizontal axis and the vertical axis arerespectively the same as those in FIG. 5. In addition, the half-presssignal S1 and the full-press signal S2 are activated at the same time.However, it is assumed that the subject is moving.

Referring to FIG. 9, the AF operation starts by the activation of thehalf-press signal S1 at a time t0, thereby driving the focus lens 104 ata high, constant speed to perform operation A of FIG. 3A. When a peakvalue of AF evaluation values is detected, the focus lens 104 is drivenin a reverse direction at a low, constant speed to perform operation Bof FIG. 3B. The peak value of the AF evaluation values is detected byoperation B.

Thereafter, operation C of FIG. 3C is performed by reversing the drivingdirection of the focus lens 104. In the current embodiment, duringoperation C of FIG. 3C, a capture preparation operation starts at a timet1. That is, the shutter 203 in a usual open state is changed to aclosed state, and the iris 107 is controlled. An interval between t1 andt2 for driving the shutter 203 and the iris 107 is a light exposurepreparation interval. In addition, the display unit 206 stops displayingan image. During the capture preparation operation, operation C of FIG.3C and operation D of FIG. 3D for removing a backlash are performed.When the operation D of FIG. 3D ends, the AF operation ends.

When the capture preparation operation ends at a time t2, the shutter203 is open, thereby starting light exposure of the image pickup device204. That is, an image is captured. Thereafter, the shutter 203 isclosed at a time t3. Thereafter, information of the image pickup device204 is read. After reading the information, the shutter 203 and the iris107 are open again at a time t4.

After the series of operations, in a case of continuous photographing,the next photographing starts at a time t5, wherein the digitalphotographing apparatus 1 performing AF first of all performs the AFoperation at this time. In the current embodiment, a peak positiondetection operation is performed three times. Calculation of the movingspeed of the subject according to detecting the peak position threetimes may be performed using the method described with reference to FIG.6. Of course, when the subject does not move, the AF operation may becompleted by one peak position detection operation.

In detail, an in-focus position in image capturing is predicted byperforming the moving body prediction AF before a light exposurepreparation interval, i.e., an interval between t5 and t6. Thereafter,compensation driving of the focus lens 104 towards an in-focusprediction position FOCUS5 is performed by performing moving bodycompensation driving in the light exposure preparation interval, i.e.,an interval between t6 and t7. Specifically, the moving bodycompensation driving may be performed until driving of the shutter 203to a closed state is completed. In the current embodiment, the movingspeed of the subject is calculated from information regarding lenspositions FOCUS2 to FOCUS4 and time information thereof, the lensposition FOCUS5 is calculated from the moving speed of the subject, andoperations C and D as the AF operation are performed towards thecalculated lens position FOCUS5.

Unless the continuous photographing ends, the above-described operationsare repeated. The wobbling operation may be performed to detect a peakposition in the continuous photographing.

In the current embodiment, driving the focus lens 104 to detect a peakposition when the shutter 203 is in the usual open state during thecontinuous photographing is performed by a combination of operation Aand operation B at a low speed as the AF operation. Alternatively, thedriving of the focus lens 104 may be performed by a combination ofoperation B and operation C.

When the moving speed Sv0 of the subject has been detected before thefirst image of the continuous photographing is captured and the movingspeed Sv0 is slow, an average value Sv=(Sv0+Sv1)/2 of the moving speedSv0 and the moving speed Sv1 acquired after the first image is capturedis obtained and may be used for the moving body prediction AF and themoving body compensation driving from a second image capture. An averagevalue of moving speeds of a subject is performed because, when thesubject is far away and the magnification on the image surface is low,the image surface speed is also slow, and accordingly an error may occurin speed detection. Furthermore, when continuous photographing of asubject of which an image surface speed is slow is continuouslyperformed, an average value Sv=(Sv1+Sv2)/2 of the moving speed Sv1 in aprevious capture and the moving speed Sv2 in a current capture may beused for the moving body prediction AF and the moving body compensationdriving.

FIG. 10 is a timing diagram indicating a moving body compensationdriving method according to another embodiment of the invention. Thecurrent embodiment will be described with respect to how it differs fromthe embodiment of FIG. 9.

Referring to FIG. 10, in the current embodiment, when it is detectedthat a subject is moving before light exposure for capturing a firstimage of continuous photographing, immediately after the light exposurefor capturing the first image is completed at the time t3, the movingbody compensation driving for capturing a second image of the continuousphotographing is performed by using an already acquired moving speed ofthe subject

The focus lens 104 is driven from the lens position FOCUS1 adjusted tocapture the first image to the lens position FOCUS2 in an interval inwhich the shutter 203 starts to transition to the usual open state afterthe light exposure for capturing the first image is completed, i.e., aninterval between t3 and t4. In this case, the lens position FOCUS2 ofthe focus lens 104 is obtained as follows.

From the moving speed Sv of the subject, which is acquired until theimage of the continuous photographing, and a time Tf from a lightexposure start time to a time for driving the shutter 203 to the usualopen state, a moving amount ΔR0 of the subject for Tf is obtained. Anequation to obtain ΔR0 is ΔR0=Sv*Tf. Then, the lens position FOCUS2 isobtained by FOCUS2=FOCUS1+R0.

As described above, by performing the moving body compensation drivingin advance of the moving body prediction AF according to the embodimentof FIG. 9, an AF operation time after the first image of the continuousphotographing is captured may be reduced.

FIG. 11 is a timing diagram indicating a moving body compensationdriving method according to another embodiment of the invention. In thecurrent embodiment, an actuator with no backlash by using VCM or thelike is used, and a system with no backlash even in position detectionby detecting a position of the focus lens 104 optically is used.

In the current embodiment, peak positions acquired in both directions ofthe operations B and C in the AF operation are used to detect the movingspeed of a subject. That is, the moving speed of the subject is obtainedby the above-described equation Sv=(B1−C1)/T1. Here, a dashed linebetween FOCUS1 and FOCUS2 and a dashed line between FOCUS4 and FOCUS5are lines indicating positions at which the focus lens 104 changes itsmoving direction and are irrelevant to the focal position. In addition,it is reconfirmed during operation B that the subject is a moving body,and a capture preparation operation starts. In operation B, the movingbody compensation driving is performed, thereby moving the focus lens104 to a focal position in image capturing.

Because there is no backlash in the current embodiment, operation D forremoving the backlash is omitted.

FIG. 12 is a timing diagram indicating a moving body compensationdriving method according to another embodiment of the invention. In thecurrent embodiment, although the moving body compensation driving doesnot have to be performed in capturing a first image of continuousphotographing because an initial moving speed of a subject is slow, itis predicted after capturing the first image that a position of thesubject is over a depth of field (DOF), causing a change of an image onan image surface.

Referring to FIG. 12, a first image of continuous photographing iscaptured in an interval between t0 and t3 without performing the movingbody compensation driving. The moving body compensation driving isperformed in an interval between t3 and t4 to capture the next image inan interval in which AF evaluation values cannot be calculatedimmediately after capturing the first image, i.e., in a state wherelight does not arrive at the image pickup device 204. In an interval inwhich AF evaluation values can be calculated, a scanning operationaccording to a back-and-forth operation is performed, for example, threetimes, and the moving speed of the subject is detected from a change ofa peak position of AF evaluation values in an interval between t5 andt6. Thereafter, the moving body compensation driving is performed in aninterval between t6 and t7 before a second image of the continuousphotographing is captured.

Even if the actual moving speed of the subject is constant, an imagesurface speed of the object is faster than before from capturing a thirdimage of the continuous photographing. Thus, to respond to this fastspeed, the back-and-forth scanning operation for detecting a peakposition is limited to one time. Then, a moving speed of the subject maybe obtained from a peak position acquired in a previous capturingoperation and a peak position acquired by one back-and-forth scanningoperation in a current capturing operation.

When a fourth image of the continuous photographing is captured, themoving speed of the subject is obtained from the peak position acquiredby the one back-and-forth scanning operation in the third imagecapturing operation and a peak position acquired by one back-and-forthscanning operation in a current capturing operation. For example, if itis assumed that the time between capturing operations in continuousphotographing is tc1 and peak positions acquired by one back-and-forthscanning operation in the capturing operations are Bc1 and Bc2, themoving speed Scv of a subject may be obtained by Scv=(Bc1−Bc2)/tc1.

Accordingly, by reducing the time taken for the moving body predictionAF and the moving body compensation driving, the continuousphotographing speed may be increased.

Although the moving body prediction AF operation is changed from threeback-and-forth scanning operations to one back-and-forth scanningoperation in the middle of the moving body prediction AF in the currentembodiment, the invention is not limited thereto. For example, when thespeed of continuous photographing is important, if it is determined thatthe subject is moving, a peak position is obtained by performing onlyone back-and-forth scanning operation, and in capturing from a thirdimage, the moving speed of the subject may be obtained from a pluralityof peak positions acquired by the one back-and-forth scanning operation.

In addition, when the subject moves at a low speed on an image surfaceduring continuous photographing, the moving speed of the subject may beobtained from peak positions acquired by performing a back-and-forthscanning operation two or three times, and when the subject moves at ahigh speed on the image surface during the continuous photographing, thenumber of back-and-forth scanning operations may be reduced according tothe moving speed of the subject, such that a peak position is acquiredby performing the back-and-forth scanning operation once.

FIG. 13 is a timing diagram indicating a moving body compensationdriving method according to another embodiment of the invention. In thecurrent embodiment, an electronic front curtain shutter is used insteadof a mechanical shutter used in FIG. 12. Because the electronic frontcurtain shutter is well-known technology, a detailed description thereofis omitted, and the current embodiment will be described with respect tohow it differs from the embodiment of FIG. 12.

Referring to FIG. 13, the image pickup device 204 transmits an imagesignal generated by an operation of selectively reading electric chargesto the display unit 206 to display a live-view image. The AF operationstarts by the half-press signal S1, and the capture preparationoperation is performed in a light exposure preparation interval by thefull-press signal S2 (between t0 and t2). That is, the display unit 206stops displaying according to the operation of selectively readingelectric charges, the shutter 203 is closed, and the iris 107 iscontrolled. At this time, because only a rear curtain is a mechanicalshutter in the current embodiment, the rear curtain is changed to aclosed state. However, because the rear curtain is a shutter forblocking light after a front curtain is driven, the closed state of therear curtain indicates a state of transitioning to a positionimmediately before light is blocked.

Thereafter, light exposure starts by driving the front curtain. Becausethe front curtain is an electronic front curtain in the currentembodiment, a reset timing signal RESET is applied to the image pickupdevice 204, thereby starting the light exposure at the time t2. Thelight exposure replaces a mechanical front curtain by sequentiallyresetting the image pickup device 204 from the top to the bottom. At thetiming when the light exposure ends, the rear curtain is driven, therebyblocking the light incident on the image pickup device 204. Electriccharges accumulated by the image pickup device 204 are read, and theimage pickup device 204 is blocked from light by the rear curtain duringthe reading.

After the data reading ends, the rear curtain is in an open state again,and a scanning operation for acquiring AF evaluation values by receivinglight in the image pickup device 204 is performed. Because a method ofobtaining a moving speed of a subject thereafter is the same as that ofFIG. 12, a detailed description thereof is omitted.

FIG. 14 is a timing diagram indicating a moving body compensationdriving method according to another embodiment of the invention. In thecurrent embodiment, a global shutter in which a shutter function isincluded in the image pickup device 204 is used instead of a mechanicalshutter used in FIG. 12. The global shutter starts light exposure bysimultaneously resetting electric charges with respect to a whole screenand ends the light exposure by simultaneously transmitting accumulatedelectric charges to the light non-exposure part with respect to thewhole screen. Because the global shutter is well-known technology, adetailed description thereof is omitted, and the current embodiment willbe described with respect to how it differs from the embodiment of FIG.12.

Referring to FIG. 14, the image pickup device 204 transmits an imagesignal generated by an operation of selectively reading electric chargesto the display unit 206 to display a live-view image. The AF operationstarts by the half-press signal S1, and the capture preparationoperation is performed in a light exposure preparation interval by thefull-press signal S2 (between t0 and t2). That is, the display unit 206stops displaying according to the operation of selectively readingelectric charges, and the iris 107 is controlled.

Thereafter, light exposure starts by driving a front curtain. Becausethe front curtain is an electronic front curtain in the currentembodiment, a reset timing signal RESET is applied to the image pickupdevice 204, thereby starting the light exposure at the time t2. Indetail, the light exposure starts by simultaneously applying the resettiming signal RESET to a whole screen of the image pickup device 204.The light exposure ends by simultaneously applying an electric chargetransfer signal TRANSFER to the whole screen of the image pickup device204 at a time t3.

Electric charges accumulated by the image pickup device 204, i.e., animage signal, are read by a data read signal DATA READ. While the datareading is being performed, a gate is closed so that a new electriccharge does not flow to an electric charge storage unit (not shown) inwhich transmitted electric charges are stored even if the image pickupdevice 204 receives light. That is, the image pickup device 204 is inthe same state as a light-blocked state.

When the reading of data from the electric charge storage unit ends,continuous photographing is performed by repeatedly resetting andtransmitting electric charges. Because a method of obtaining the movingspeed of a subject thereafter is the same as that of FIG. 12, a detaileddescription thereof is omitted.

[Method of Controlling the Digital Photographing Apparatus 1]

FIG. 15 is a flowchart illustrating a method of controlling the digitalphotographing apparatus 1, according to an embodiment of the presentinvention. FIG. 15 illustrates an operation (operation 1) of startingthe digital photographing apparatus 1.

Referring to FIG. 15, when the digital photographing apparatus 1 startsoperating by turning the main switch of the digital photographingapparatus 1 on, a manipulation of the manipulation unit 207 is detectedin operation S101. According to the detection, a mode of the digitalphotographing apparatus 1 is set in operation S102. In operation S103,lens information for operating the digital photographing apparatus 1 isreceived from the lens 100 and stored. The lens information includesvarious kinds of lens-unique parameters and may be information forcontrolling AF, AE, AWB, and image quality. While the lens informationis received from the lens 100 in the digital photographing apparatus 1using the exchangeable lens 100, as shown in FIG. 1, operation S103 maybe skipped in digital photographing apparatuses such as a camera orother device with a non-exchangeable lens.

In operation S104, the image pickup device 204 starts periodicphotographing. In operation S105, the image pickup device 204 performslight measurement to calculate AE and AWB. In operation S106,periodically captured images are displayed as live-view images.

It is determined in operation S107 whether the main switch is turnedoff. If the main switch is not turned off, operations S101 to S106 arerepeated. Otherwise, if the main switch is turned off, the operation ofthe digital photographing apparatus 1 stops in operation S108.Accordingly, operation 1 ends.

FIGS. 16 and 17 are flowcharts illustrating a method of controlling thedigital photographing apparatus 1, according to another embodiment ofthe invention. FIGS. 16 and 17 illustrate an operation (operation 2)performed by applying the half-press signal S1 due to a halfway press ofthe shutter release button during a live-view display.

Referring to FIGS. 16 and 17, when the half-press signal S1 is applied,the digital photographing apparatus 1 commands to drive the focus lens104 in a second direction at a high, constant speed by an interruptoperation in operation S201. That is, operation A of the AF operation isperformed. In operation S202, an AF evaluation value is calculated whiledriving the focus lens 104. It is determined in operation S203 whetherthe AF evaluation value has passed a peak. If the AF evaluation valuehas not passed the peak, the digital photographing apparatus 1 proceedsback to operation S202. Otherwise, if the AF evaluation value has passedthe peak, a moving body prediction flag is reset in operation S204. Thisis an initial setting value of the moving body prediction flag.

In operation S205, the digital photographing apparatus 1 commands todrive the focus lens 104 in a first direction at a low, constant speedby changing the driving direction. That is, operation B of the AFoperation is performed. In operation S206, an AF evaluation value iscalculated. Then, it is determined in operation S207 whether the AFevaluation value has passed a peak. If the AF evaluation value has notpassed the peak, the digital photographing apparatus 1 proceeds back tooperation S206. Otherwise, if the AF evaluation value has passed thepeak, a peak position B0 is stored in operation S208.

In operation S209, the digital photographing apparatus 1 commands todrive the focus lens 104 in the second direction at a high, constantspeed again to remove backlash. That is, operation C of the AF operationis performed. In operation S210, an AF evaluation value is calculated.Then, it is determined in operation S211 whether the AF evaluation valuehas passed a peak. If the AF evaluation value has not passed the peak,the digital photographing apparatus 1 proceeds back to operation S210.Otherwise, if the AF evaluation value has passed the peak, the focuslens 104 is driven towards the peak position B0 in the first directionat a high speed in operation S212. That is, operation D of the AFoperation is performed. At this time, an AF evaluation value does nothave to be calculated. The AF operation is completed by theabove-described procedures, and it is indicated in operation S213 thatthe AF operation has successfully ended.

Even after the AF operation successfully ends, AF evaluation values arecontinuously calculated in operation S214. Then, it is determined inoperation S215 whether a change in the AF evaluation values exists. If achange in the AF evaluation values does not exist, the digitalphotographing apparatus 1 maintains the focus lens 104 in the currentstate and waits for the full-press signal S2 according to a full pressof the shutter release button while repeatedly performing operationS214. Otherwise, if a change in the AF evaluation values exists, it isdetermined that the subject has been changed. That is, it is determinedthat the subject is possibly moving.

If it is determined in operation S215 that a change in the AF evaluationvalues exists, the digital photographing apparatus 1 commands to drivethe focus lens 104 in the second direction at a low, constant speed inoperation S216. In operation S217, an AF evaluation value is calculatedwhile driving the focus lens 104. It is determined in operation S218whether the AF evaluation value has passed a peak while driving thefocus lens 104 within a reference amount or whether the focus lens 104has been driven over the reference amount.

If the above conditions are not satisfied, the digital photographingapparatus 1 proceeds back to operation S217. Otherwise, if any of theabove conditions is satisfied, the digital photographing apparatus 1commands to drive the focus lens 104 in the first direction at a low,constant speed in operation S219. In operation S220, an AF evaluationvalue is calculated while driving the focus lens 104.

It is determined in operation S221 whether the AF evaluation value haspassed a peak while driving the focus lens 104 within the referenceamount or whether the focus lens 104 has been driven over the referenceamount, as in operation S218.

If the above conditions are not satisfied, the method proceeds back tooperation S220. Otherwise, if any of the above conditions is satisfied,the peak position B1 shown in FIG. 6 is acquired in operation S222. Itis determined in operation S223 whether B0 is identical to B1. If B0 isidentical to B1 the method proceeds back to operation S213. Otherwise,if B0 is different from B1 or if no peak is acquired, the digitalphotographing apparatus 1 proceeds to operation A21.

If B0 is different from B1 or no peak is acquired in operation S223, thedigital photographing apparatus 1 commands to drive the focus lens 104in the second direction at a low, constant speed in operation S231. Inoperation S233, an AF evaluation value is calculated again. It isdetermined in operation S233 whether the AF evaluation value has passeda peak while driving the focus lens 104 within the reference amount orwhether the focus lens 104 has been driven over the reference amount, asin operation S218. If the above conditions are not satisfied, thedigital photographing apparatus 1 proceeds back to operation S232.Otherwise, if any of the above conditions is satisfied, the peakposition C1 shown in FIG. 6 is acquired in operation S234.

It is determined in operation S235 whether B1 is identical to a sum ofC1 and an error BKL due to backlash. If B1 is identical to the sum of C1and the error BKL, the digital photographing apparatus 1 determines thatthe subject has not moved and proceeds back to operation S204. Here, B1does not have to be numerically identical to the sum of C1 and the errorBKL, and if B1 is substantially the same as the sum of C1 and the errorBKL or if a difference between B1 and the sum of C1 and the error BKL iswithin a predetermined error range, it may be determined that B1 isidentical to the sum of C1 and the error BKL. Otherwise, if B1 isdifferent from the sum of C1 and the error BKL, the digitalphotographing apparatus 1 commands to drive the focus lens 104 in thefirst direction at a low, constant speed in operation S236. In operationS237, an AF evaluation value is calculated while driving the focus lens104.

It is determined in operation S238 whether the AF evaluation value haspassed a peak while driving the focus lens 104 within the referenceamount or whether the focus lens 104 has been driven over the referenceamount, as in operation S218. If the above conditions are not satisfied,the digital photographing apparatus 1 proceeds back to operation S237.Otherwise, if any of the above conditions is satisfied, the peakposition B2 shown in FIG. 6 is acquired in operation S239.

It is determined in operation S240 whether B2 is acquired. If B2 is notacquired, it is determined that the possibility that the digitalphotographing apparatus 1 is in a panning state is high, and the digitalphotographing apparatus 1 proceeds back to operation S204 to perform theAF operation again. Otherwise, if B2 is acquired, it is determined thatthe subject is moving, and the moving speed of the subject and acompensation amount for the moving body compensation driving arecalculated in operation S241. The moving speed of the subject and thecompensation amount may be obtained by Sv=(B1−B2)/T1 and AB3=Sv*T2,respectively.

In operation S242, the moving body prediction flag is set. In operationS243, the digital photographing apparatus 1 commands to drive the focuslens 104 in the second direction at a low speed, wherein the moving bodycompensation driving is performed by ΔB3. Thereafter, the digitalphotographing apparatus 1 proceeds back to operation S232.

FIGS. 18, 19A, and 19B are flowcharts illustrating a method ofcontrolling the digital photographing apparatus 1, according to anotherembodiment of the invention. FIGS. 18, 19A, and 19B illustrate anoperation (operation 3) performed by applying the full-press signal S2by a full press of the shutter release button while moving body trackingis being repeated. When the half-press signal S1 and the full-presssignal S2 are turned on from the beginning, operation 3 starts after aninitial in-focus is determined, i.e., after operations A and B of the AFoperation end.

Referring to FIGS. 18, 19A, and 19B, in operation S301, the display unit206 is turned off, the shutter 203 is in a closed state by driving theshutter 203 to block light incident on the image pickup device 204, andthe iris 107 is driven to a proper iris value. In operation S302, it isdetermined whether the moving body prediction flag is set.

If the moving body prediction flag is not set, the digital photographingapparatus 1 proceeds to operation S305. Otherwise, if the moving bodyprediction flag is set, a compensation value AR is obtained by ΔR=Sv*Tin operation S303, and a peak position is compensated for by ΔR inoperation S304.

In operation S305, the focus lens 104 is driven in the second and firstdirections at a high speed to move to the peak position. In operationS306, it is determined whether driving the shutter 203 and the iris 107is completed. In the current embodiment, although the operating time ofoperation S305 is designed to be shorter than the driving time of theshutter 203 and the iris 107, the invention is not limited thereto. Forexample, if the operating time of operation S305 is longer than thedriving time of the shutter 203 and the iris 107, whether operation S305has ended may be simultaneously determined when operation S306 isperformed.

If it is determined in operation S306 that driving the shutter 203 andthe iris 107 is not completed, the digital photographing apparatus 1proceeds back to operation S305. Otherwise, if it is determined inoperation S306 that driving the shutter 203 and the iris 107 iscompleted, light exposure starts in operation S307. When the lightexposure ends, data is read in operation S308. The read data is appliedto the camera controller 209, wherein the camera controller 209 performssignal processing on the read data and captures the read data as a stillimage.

If a subject is moving, in continuous photographing, a moving bodycompensation is performed for the next capturing after the currentcapturing. By doing this, the continuous photographing speed mayincrease. This process corresponds to operations S309 to S311.

In operation S309, it is determined whether the moving body predictionflag is set. If the moving body prediction flag is not set, the digitalphotographing apparatus 1 proceeds to operation S312. Otherwise, if themoving body prediction flag is set, a moving amount ΔR0 of the subjectis obtained by ΔR0=Sv*Tf in operation S310. The moving amount ΔR0corresponds to a moving body compensation driving amount immediatelyafter light exposure, as shown in FIG. 10. In operation S311, the focuslens 104 is driven in the second and first directions at a high speed tomeet a peak position compensated for by ΔR0.

In operation S312, it is determined whether the data reading has ended.At this time, operation S312 may be simultaneously performed withdetermining whether the moving body compensation driving has ended. Ifthe data reading has ended, driving for opening the shutter 203 anddriving for returning the iris 107 to an open state are performed, andthe display unit 206 is turned on in operation S313. In operation S314,the moving body prediction flag is reset. Although the moving bodyprediction flag is first reset under an assumption that the subject isnot moving in the current embodiment, the invention is not limitedthereto. For example, the moving body prediction flag may not be resetduring continuous photographing, and this case is advantageous when asubject is moving at a high speed.

After the moving body prediction flag is reset, AF evaluation values arecalculated again in operation S315. Then, it is determined in operationS316 whether a change in the AF evaluation values exists. Whether achange in the AF evaluation values exists may be determined from morethan two AF evaluation values. However, the invention is not limitedthereto. If a change in the AF evaluation values does not exist, it isdetermined that a peak position in next capturing is the same as a peakposition in previous capturing, and the digital photographing apparatus1 proceeds back to operation S301. Otherwise, if a change in the AFevaluation values exists, it is determined that the subject is moving orthe digital photographing apparatus 1 is in the panning state, and thedigital photographing apparatus 1 proceeds to an operation A31.

Otherwise, if it is determined in operation S316 that a change in the AFevaluation values exists, the same operations as operations S216 to S223of FIG. 16 are performed. Thereafter, if it is determined in operationS324 that a previous peak position B0 is the same as a current peakposition B1, the digital photographing apparatus 1 proceeds back tooperation S301 to perform a capturing operation. Otherwise, if it isdetermined in operation S324 that the previous peak position B0 isdifferent from the current peak position B1, a peak position C1 isacquired by performing operation C as in operations S231 to S240 of FIG.17. However, if it is determined in operation S329 that B1 is the sameas C1+BKL, the digital photographing apparatus 1 proceeds back tooperation S301. Otherwise, if it is determined in operation S329 that B1is different from C1+BKL, a peak position B2 is acquired by performingoperation C in operations S330 to S333.

If it is determined in operation S334 that B2 is not acquired, it isdetermined that the possibility that the digital photographing apparatus1 is in the panning state is high, and the digital photographingapparatus 1 proceeds back to operation S317 to detect a peak positionagain. Otherwise, if it is determined in operation S334 that B2 isacquired, a moving speed Sv of the subject is obtained by Sv=(B1−B2)/T1in operation S335.

In the current embodiment, Sv is obtained by using B1 and B2 obtained inthe same shutter open interval between successive capturing operations.However, as in the embodiments described with reference to FIGS. 12, 13,and 14, the moving speed Sv of a subject may be obtained from B1obtained in previous capturing and B2 obtained before current capturing.In addition, when a subject is moving at a low speed, the moving speedof the subject may be obtained according to the flowcharts of FIGS. 19Aand 19B, and when a subject is moving at a high speed, the moving speedof the subject may be obtained from B1 obtained in previous capturingand B2 obtained before current capturing. As described above, a methodof obtaining the moving speed of a subject may vary according to themoving speed of the subject. In addition, the moving speed of a subjectmay be calculated by using a second or higher order equation.

When the calculation of the moving speed of the subject is completed,the moving body prediction flag is set in operation S336, and thedigital photographing apparatus 1 proceeds back to operation S301.

FIGS. 20A and 20B are flowcharts illustrating another embodiment of anoperation A32 a of FIG. 19B. In the current embodiment, the moving speedof a subject is obtained by using three pieces of information B1, B2,and B3 as described with reference to FIG. 9. The current embodimentwill be described with respect to how it differs from operation A32 a ofFIG. 19B.

Referring to FIGS. 20A and 20B, operations S401 to S409 are the same asoperations S325 to S333 of FIG. 19B. In operation S410, the moving speedSv1 of a subject is obtained from B1 and B2. Sv1 may be obtained by(B1−B2)/T1. As described above, in operations S411 to S419, a peakposition B3 is obtained by performing a scanning operation from B2 toB3.

If it is determined in operation S420 that B3 is not acquired, it isdetermined that the digital photographing apparatus 1 is in the panningstate, and the digital photographing apparatus 1 proceeds back tooperation S317 to perform an AF scanning operation again. Otherwise, ifit is determined in operation S420 that B3 is acquired, the moving speedSv2 of the subject is obtained from B2 and B3 in operation S421. This isthe moving speed of the subject from B2 to B3 of FIG. 6. Sv2 is obtainedby (B2−B3)/T2. Thereafter, the average value Sv of the moving speeds isobtained by (Sv1+Sv2)/2. After the average moving speed of the subjectis obtained, a compensation amount ΔB4 for the moving body compensationdriving is obtained by Sv*T3 in operation S421.

In operation S422, the moving body prediction flag is set, and thedigital photographing apparatus 1 proceeds back to operation S301 toperform capturing through the moving body compensation driving.

FIG. 21 is a flowchart illustrating another embodiment of operation A31of FIGS. 19A and 19B. The current embodiment illustrates a method ofperforming moving body prediction AF by using the wobbling operation.

Referring to FIG. 21, in operation S501, the focus lens 104 is driven inthe first direction by a very small amount of nFδ/2. Here, n may be anumber of about 1 to 3, F denotes an iris value, δ denotes an allowablecircle of confusion of the digital photographing apparatus 1, and Fδdenotes a DOF. In operation S502, an AF evaluation value V1 is acquired.

In operation S503, the focus lens 104 is driven in the second directionby a very small amount of nFδ. In operation S504, an AF evaluation valueV2 is acquired.

In operation 505, it is determined whether V1 is the same as V2. If V1is the same as V2, it is determined that the subject is not moving, andthe digital photographing apparatus 1 proceeds back to operation S301 toperform a capturing operation. Otherwise, if V1 is different from V2,the focus lens 104 is driven in the first direction by a very smallamount of nFδ in operation S506, and an AF evaluation value iscalculated in operation S507.

In operation S508 it is determined whether the calculated AF evaluationvalue has passed a peak position. If it is determined that thecalculated AF evaluation value has not passed a peak position, thedigital photographing apparatus 1 proceeds back to operation S506. Ifthe subject is not moving, the calculated AF evaluation value hasgenerally passed a peak position, and if the calculated AF evaluationvalue has not passed a peak position, it is obvious that the subject ismoving. Thus, if it is determined that the calculated AF evaluationvalue has passed a peak position, the peak position B1 is acquired inoperation S509.

In operations S510 to S512, it is determined whether an AF evaluationvalue has passed a peak position, by driving the focus lens 10 in thesecond direction. In operations S513 to S515, it is determined whetheran AF evaluation value has passed a peak position, by driving the focuslens 10 in the first direction.

In operation S516, a peak position B2 is acquired, and in operationS517, a moving speed Sv (=(B1−B2)/T1) of the subject and a drivingamount ΔB3(=Sv*T2) for moving body compensation are obtained. Inoperation S518, the moving body prediction flag is set, and the digitalphotographing apparatus 1 proceeds back to operation S301.

As described above, the digital photographing apparatus 1 according tothe embodiments of the invention may capture images by correctly andquickly focusing a subject by performing moving body prediction AF andmoving body compensation driving when the subject is moving.

A program for executing a driving method according to theabove-described embodiments and their modifications in the digitalphotographing apparatus 1 may be stored in a computer-readable recordingmedium (not shown).

The system or systems described herein may be implemented on any form ofcomputer or computers and the components may be implemented as dedicatedapplications or in client-server architectures, including a web-basedarchitecture, and can include functional programs, codes, and codesegments. Any of the computers may comprise a processor, a memory forstoring program data and executing it, a permanent storage such as adisk drive, a communications port for handling communications withexternal devices, and user interface devices, including a display,keyboard, mouse, etc. When software modules are involved, these softwaremodules may be stored as program instructions or computer readable codesexecutable on the processor on a computer-readable media such asread-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetictapes, floppy disks, and optical data storage devices. The computerreadable recording medium can also be distributed over network coupledcomputer systems so that the computer readable code is stored andexecuted in a distributed fashion. This media is readable by thecomputer, stored in the memory, and executed by the processor.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedas incorporated by reference and were set forth in its entirety herein.

For the purposes of promoting an understanding of the principles of theinvention, reference has been made to the preferred embodimentsillustrated in the drawings, and specific language has been used todescribe these embodiments. However, no limitation of the scope of theinvention is intended by this specific language, and the inventionshould be construed to encompass all embodiments that would normallyoccur to one of ordinary skill in the art.

The embodiments herein may be described in terms of functional blockcomponents and various processing steps. Such functional blocks may berealized by any number of hardware and/or software components thatperform the specified functions. For example, the described embodimentsmay employ various integrated circuit components, e.g., memory elements,processing elements, logic elements, look-up tables, and the like, whichmay carry out a variety of functions under the control of one or moremicroprocessors or other control devices. Similarly, where the elementsof the described embodiments are implemented using software programmingor software elements the invention may be implemented with anyprogramming or scripting language such as C, C++, Java, assembler, orthe like, with the various algorithms being implemented with anycombination of data structures, objects, processes, routines or otherprogramming elements. Functional aspects may be implemented inalgorithms that execute on one or more processors. Furthermore, theembodiments of the invention could employ any number of conventionaltechniques for electronics configuration, signal processing and/orcontrol, data processing and the like. The words “mechanism” and“element” are used broadly and are not limited to mechanical or physicalembodiments, but can include software routines in conjunction withprocessors, etc.

The particular implementations shown and described herein areillustrative examples of the invention and are not intended to otherwiselimit the scope of the invention in any way. For the sake of brevity,conventional electronics, control systems, software development andother functional aspects of the systems (and components of theindividual operating components of the systems) may not be described indetail. Furthermore, the connecting lines, or connectors shown in thevarious figures presented are intended to represent exemplary functionalrelationships and/or physical or logical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships, physical connections or logical connectionsmay be present in a practical device. Moreover, no item or component isessential to the practice of the invention unless the element isspecifically described as “essential” or “critical”.

The use of “including,” “comprising,” or “having” and variations thereofherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Unless specified or limitedotherwise, the terms “mounted,” “connected,” “supported,” and “coupled”and variations thereof are used broadly and encompass both direct andindirect mountings, connections, supports, and couplings. Further,“connected” and “coupled” are not restricted to physical or mechanicalconnections or couplings. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) should be construed to cover both the singular and theplural. Furthermore, recitation of ranges of values herein are merelyintended to serve as a shorthand method of referring individually toeach separate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated into the specificationas if it were individually recited herein. Finally, the steps of allmethods described herein are performable in any suitable order unlessotherwise indicated herein or otherwise clearly contradicted by context.The use of any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. Numerous modifications and adaptations will bereadily apparent to those skilled in this art without departing from thespirit and scope of the invention.

What is claimed is:
 1. A photographing apparatus comprising: a focuslens; a focus lens driver for driving the focus lens; an image pickupdevice for generating an image signal by picking up light which haspassed through the focus lens; a processor for determining a focalposition of the focus detection; a shutter for controlling lightexposure of the image pickup device; an iris; and an iris drivingactuator for driving the iris, wherein the processor determines adriving direction of the focus lens based on at least two image frameswhich are obtained on different focal positions from each other beforecapturing of a still image to be stored in a memory card, the at leasttwo image frames are obtained while displaying a live-view image, andthe iris driving actuator opens the iris while obtaining the at leasttwo image frames, and adjusts the iris to a calculated iris value beforethe still image to be stored in the memory card is captured.
 2. Thephotographing apparatus of claim 1, wherein when it is determined that amovement of the object exists, the at least two image frames areobtained.
 3. The photographing apparatus of claim 1, wherein themovement of the subject includes a movement in an optical axisdirection.
 4. The photographing apparatus of claim 1, when a continuousphotographing for continuously capturing still images is performed:after a previous still image capturing and before a light exposurepreparation interval for a subsequent still image capturing, theprocessor determines the driving direction; and the focus lens drivermoves the focus lens by the determined driving direction before thesubsequent still image capturing starts.
 5. The photographing apparatusof claim 1, wherein the processor calculates a moving speed of a subjectbased on the at least two image frames, and the focus lens driver movesthe focus lens in order to obtain the at least two image frames based onthe calculated moving speed.
 6. The photographing apparatus of claim 1,wherein the processor determines the driving direction based on apre-stored information related to focusing.
 7. The photographingapparatus of claim 1, wherein the shutter is a mechanical shutterincluding a front curtain and a rear curtain.
 8. The photographingapparatus of claim 1, wherein the shutter is an electronic front curtainshutter including an electronic front curtain for beginning lightexposure by resetting electric charges and a mechanical rear curtain forending the light exposure.
 9. The photographing apparatus of claim 1,wherein the moving of the focus lens in the determined driving directionis performed in an interval before beginning to drive an electronicfront curtain for the subsequent image capturing after stopping drivingfor selectively reading electric charges from the image pickup device.10. The photographing apparatus of claim 1, wherein the shutter is aglobal shutter including an electronic front curtain for beginning lightexposure by resetting electric charges and an electronic rear curtainfor ending the light exposure.
 11. The photographing apparatus of claim1, wherein the moving the focus lens in the determined driving directionis performed in an interval before beginning to drive an electronicfront curtain for image capturing after stopping driving for selectivelyreading electric charges from the image pickup device.
 12. Thephotographing apparatus of claim 1, wherein the at least two imageframes are obtained while displaying a live-view image, thephotographing apparatus ends the displaying of the live-view imagebefore a subsequent still image capturing, and the moving the focus lensin the determined driving direction is performed in an interval beforebeginning the image capturing after ending the displaying of thelive-view image.
 13. The photographing apparatus of claim 1, wherein thedetection of the focal position is performed by driving the focus lensback and forth.
 14. The photographing apparatus of claim 1, wherein,during a continuous photographing, detecting the focal position multipletimes is performed in an image pickup interval before a light exposurepreparation interval, and a moving speed of the subject is calculatedfrom a result of the detecting of the focal position multiple times. 15.The photographing apparatus of claim 1, wherein, during a continuousphotographing, the focal position detection is performed at least oncein a image pickup interval before a light exposure preparation intervalfor every still image capturing, and a moving speed of the subject iscalculated by using a focal position result detected in the image pickupinterval for current still image capturing and a focal position resultdetected in the image pickup interval for the previous still imagecapturing.
 16. The photographing apparatus of claim 1, wherein during acontinuous photographing, a moving speed of the subject is determined byusing the moving speed of the subject acquired before the continuousphotographing starts or a moving speed of the subject obtained in theprevious still image capturing during the continuous photographing. 17.The photographing apparatus of claim 1, wherein, when a moving speed ofthe subject before a continuous photographing starts is acquired, theacquired moving speed and the moving speed of the subject acquiredduring the continuous photographing are used to predict a focal positionin the subsequent still image capturing, and when the moving speed ofthe subject before the continuous photographing starts is not acquired,the moving speed of the subject acquired during the continuousphotographing is used to predict a focal position in the subsequentimage capturing.
 18. The AF adjusting apparatus of claim 1, wherein,when a moving speed of the subject is acquired, the moving the focuslens in the determined driving direction is performed by predicting thefocal position according to movement of the subject in an interval froma light exposure end time to an image pickup start time before the lightexposure preparation interval for the subsequent still image capturingby using the acquired moving speed.
 19. A method for controlling aphotographing apparatus comprising: obtaining at least two image frameson different focal positions from each other before capturing of a stillimage to be stored in a memory card; determining a driving direction ofa focus lens based on the obtained at least two image frames; capturinga still image to be stored in a memory card, wherein the at least twoimage frames are obtained while displaying a live-view image, and aniris is open while the at least two image frames are obtained, and isadjusted to a calculated iris value before the still image to be storedin the memory card is captured.